The present invention relates to astronomical telescopes, and more particularly, to a system that will automatically point a telescope at a selected location in the sky and automatically track that location.
Numerous designs have been provided in the prior art for mounting astronomical telescopes. One well known type is referred to as an "equatorial mount" which includes a rotatable polar shaft, a stationary support for the polar shaft, a rotatable declination shaft which is secured to the telescope, and a member which is secured to the polar shaft and which rotatably supports the declination shaft. In use, the polar shaft is positioned with its axis in the direction of the north star, and the telescope is initially fixed on a target star, planet or moon by rotating it on the shaft axes to a certain position.
Because of the rotation of the earth, the polar shaft must be slowly rotated in order to hold the telescope fixed on the selected object, and both automatic and manual drive mechanisms have been provided for this purpose. The automatic devices have usually included a small motor, such as a mechanical clock work or a synchronous motor, which is secured to the stationary support and is connected through gears to the polar shaft for rotating the polar shaft at sidereal rate.
A prior art automatic drive mechanism of the foregoing character has a number of drawbacks. It is a relatively complicated and expensive mechanism which cannot readily be installed by an average amateur astronomer. In addition, to obtain the necessary torque to turn the polar shaft, a rather large diameter gear must be attached to the polar shaft. Further, it is often desirable to be able to make small changes in the rate of rotation to maintain a fix on a planet or the moon and this is relatively difficult or not possible with conventional mechanisms.
Early observers used an altazimuth mounting in which one axis (altitude) was horizontal and the other (azimuth) vertical. Its problem is that both axes must be driven, and at rates that vary with the position. Given that a computer can easily handle the variable drive rates, the gain in reverting to an altazimuth mounting is enormous and becomes more important as the telescope gets bigger. Rotation about the vertical azimuth axis does not change the orientation of the telescope tube with respect to gravity, so that this motion does not change any aspect of the flexure of the support. In effect an altazimuth mounting is a fork mounting with the axis vertical so that the tines have no transverse load at all. Not only is the system much better able to support the load, but it obviates the twisting of the fork tines that makes it so difficult to design the declination axle bearings of the equatorially mounted telescope. Longer tines are now practicable and the horizontal elevation (altitude) axle can be nearer the mid-point of the telescope tube.
Heretofore nobody has provided a satisfactory means for readily orienting an altazimuth telescope mount and for overcoming the inherent difficulty of finding and tracking celestial objects with a telescope mounted in an altazimuth mount.
Japanese Pat. No. 15215 discloses a method and micro-computer based system for automatically directing an equatorial mounted astronomical telescope so as to capture a particular celestial body whose catalog name is inputted through a keyboard. The micro-computer performs the necessary calculations and drives declination and right-ascension stepping motors.
Russian Pat. No. 511559 also appears to disclose a computer based declination and right-ascension control for a telescope mount. Keyboard inputs are apparently used for some sort of correction. The system has improved tracking capability, but it does not appear that the system automatically searches for an inputted celestial object.
Various "Equatorial" telescope mounts, sidereal drives, and other marginally relevant mechanisms are disclosed in U.S. Pat. Nos. 3,893,746, 3,942,865, 3,951,511, 4,050,318, 4,285,567 and 4,541,294.